Madrid. The Earth’s magnetic field protects us from dangerous radiation from space, but 41 thousand years ago cosmic rays passed through our planet’s atmosphere.
Scientists present new information about that phenomenon of excursion
in which our planet’s magnetic field decreased and harmful space rays bombarded it.
The Earth’s magnetic field protects our planet from the attack of cosmic radiation flowing through space and at the same time from charged particles ejected by the Sun. But the geomagnetic field is not stationary. Magnetic north not only wobbles away from true north (a geographically defined location), but occasionally reverses. During these reversals, north becomes south, south becomes north, and in the process the magnetic field strength decreases.
Magnetic field excursions
But there are also something called magnetic field excursions, brief periods in which the intensity of the magnetic field decreases and the dipole (or two magnetic poles) that we know can disappear, replaced by multiple magnetic poles.
The Laschamps excursion, which took place about 41 thousand years ago, is among the best studied. It has a low magnetic field intensity that implies less protection for the Earth’s surface from harmful space rays. Periods of low magnetic field intensity could correlate with major disruptions in the biosphere.
To see when cosmic rays were intensely bombarding the Earth’s surface, scientists can measure cosmogenic radionuclides in cores of both ice and marine sediments. These special isotopes are produced by the interaction between cosmic rays and the Earth’s atmosphere; They are born from cosmic rays, that is why they are cosmogenic.
Moments of lower paleomagnetic field intensity (less shielding) should correlate with higher rates of cosmogenic radionuclide production in the atmosphere.